Repeated application of internal pressure to steel pipes may commonly result in generation of fatigue fractures (hereinafter also referred to as “internal pressure fatigue fractures”) in the steel pipes. In order to inhibit such internal pressure fatigue fractures, improvement in the internal pressure fatigue resistance properties of the steel pipes may be demanded.
Hitherto, in order to improve the internal pressure fatigue resistance properties of steel pipes, various technologies have been examined.
For example, as a method of producing a steel pipe for a cylinder tube having excellent internal pressure fatigue resistance properties, a method of producing a steel pipe for a cylinder tube is known in which, in the process of producing a steel pipe for a cylinder tube by drawing a steel pipe, heat treatment is performed at from 300° C. to 350° C. after the drawing (see, for example, Japanese Patent Application Laid-Open (JP-A) No. H4-183820).
In order to improve the fatigue resistance properties of the steel pipes, technologies to reduce residual stress of steel pipes are also known. For example, as a method of producing a steel pipe for a cylinder having reduced residual stress and excellent fatigue strength, a method of producing a steel pipe for a cylinder is known in which both ends of an original steel pipe are chucked, and then the original steel pipe is moved in one direction while rotating the original steel pipe, and then a roll is pushed on a worked portion of the original steel pipe while heating the worked portion to work the original steel pipe so that an outer diameter of the original steel pipe become constant (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-103329).